Apparatus for enameling metal articles



Dec. 30, 1930. A. G. SHERMAN ET AL 1,737,175

APPARATUS FOR ENAMELING METAL ARTICLES Filed Feb. 26, 192'? fi 262;; M

Patented Dec. 30, 1930 UNITED STATES PATENT OFFIIZEV .ALVIN G. SHERMAN,OF GROSSE POIN'IE, AND ALBERT IVIEADOWS, OF DETROIT, MICHI- GAN,ASSIGNORS TO THE DETROIT VAPOR STOVE COMPANY, OF DETROIT, MICHIGAN,

A CORPORATION OF MICHIGAN APPARATUS FOR ENAMELING- METAL ARTICLESApplication filed February 26, 1927. Serial No. 171,356.

the work has been conveyed on trucks in stacked relation to a diptank;the plates dipped and set upright without any relation to the subsequentfiring or the preceding cleaning operations, and then stored on truckspreparatory to the firing operation. In the firing operation theenamel-coated articles have usually been placed on a suitable carriagein large gangs and fedinto a muffle furnace and heated until they are ina dull redhot condition. When the articles have been fired the properlength oftime, according to the individual operator, they are thenremoved from the muffle furnace and transferred to'racks or trucks andallowed to cool. This transferring of the pipes or articles to theracks: from the firing operation has been manual and entirely dependentupon the individual operator. After a cooling operation, the trucks areWheeled to spraying booths preparatory to applying the finish enamelcoats thereto and subsequently firing the same.

Recently a continuous enameling process and apparatus has beendeveloped, such as is described in our copending application Serial No.31,811, filed May 21, 1925, which has become Patent No. 1,681,441. Inthis recent process the articles are continuously worked inpredetermined time periods, and synchronized from the time the processis first undertaken until it is finally finished. The various steps arecoordinated in capacity, speed, and distance of; travel so that they allwork together to apply the several coats of glass enamel to the articleas it travels in the line of instrumentalities. The articles are firedin a rotary electric furnace and the dipping, drips with suchfiringfurnace whereby the articles are in the proper physical and chemicalconditions and are placed in the firing furnace at a predetermined timeafter thedripping and drying whereby to obtain'best results in thefiring operation. The articles are progressively and uniformly heated inthe rotary furnace, and are taken out at a point closely adjacent wherethey are placed into the rotary furnace. These articles, when taken outof the furnace, are at a dull red heat, according to the particularfiring operation carried out, and it has been the prac' tice to placethese articles, after being directly removed from'the rotary furnace, ona suitable straightening plate. It also has been the practice for anoperator to remove such articles from the straightening plate and placethe same on a suitable coolingconveyer preparatory to inspection andinitial finish-- coat spraying. As this operation has been left entirelyup to the particular operator, it has often resulted that the articlesor plates were picked up too soon by the operator, with the result thata slight, or even a warpor sagging resulted. Furthern'iore, plates orarticles placed in upright positions for'subsequentcooling have beensubjected to still further warping or sagging, due to such verticallyhanging, when transferred from the rotary furnace to the coolingconveyers too soon.

It is the object of the present invention to interpose a medium betweenthe firing operations or after the. firing operations, where by thecorrect cooling and straightening of each and every article ispositively insured. The apparatus comprises a suitable conyeyer movinghorizontally and longitudinally, and provided with links or conveyingsurfaces which are fairly close together and of relatively heavymaterial. This conveyer is positioned betweenthe' rotary furnace and thecooling conveyers, the one end being positioned adjacent theremovalpoint of the rotary furnace, and the conveyer being of sues hotarticles being placed thereon will he properlystraightenedand cooled,and it will I be impossible for the operator to remove the tween thefurnace and secondary cooling conveyers.

Fig. 2 is a fragmentary detail view, somewhat diagrammatic, of aoonveyer that may be used in carrying out this process.

It is believed that the invention Will best be explained by describingthe stepsof operation leading up to the particular step forming the mainbasis for the presentinvention. Metal articles, particularly sheet metalarticles, and even cast iron articles, have presented many diiiicultiesin the glass enameling thereof, and a large majority of suchdifliculties, and a cause of the resulting imperfections, may be tracedlargely to the improper chemical and physical changes which arisebetween the various operations. WVhile the present invention may beutilized in various enameling systems other than the one described inapplicants above mentioned pending uniformly perfect ware. Referring toFig. 1, which is somewhat diagrammatic, the

- properly cleansed articles or plates may be dipped in the tank 1,which is known as the ground coat dipping tank. After the an ticles areproperly dipped they are immediately transferred to the conveyer 2. Thedetails of this conveyer are fully described and illustrated inapplicants said copending application, but it will be sufficient for thepresent invention to state that it is atimed conveyer adapted to receiveand position the articles vertically. i

A drying chamber is preferably provided for forcing the drying of thedipped articles, such drying chamber being designated 3. The conveyorfor receiving the dipped articles is preferably positioned to run alongclosely adjacent the one wall of the drying chamber as at 4. theclipping tank to the drying chamber may be called the dripping run. Thisdripping run portion and conveyer are so p-osi-' tioned adjacent thedrying chamber that the plates positioned on the conveyer will besubject to radiating heat from the drying chains.

ber,'so as to temporarily fix the depth of enamel coat at the propertime. a

The drying chamber 3 assists in forcing.

This run of the conveyer from the drying of the articles, and is sodesigned and operated that the articles, after being dipped and havingthe proper coatingenamel, are dried to have the proper chemical andphysical properties upon issuing from the drying chamber, thuseliminating all chances of damage to the coated surfaces due to thehumidity of the air and dust or other particles. .The properly driedarticles continuously and successively issue from the drying chamber andare presented by the conveyer to a position 5 closely adjacent thefeeding port of a firing furnace, which may be generally designated 6.

As such properly coated and dried articles are continuously andsuccessively presented, they must be removed by the workmen, andimmediately placed in the firing oven. Each piece is therefore uniformwith respect to physical and chemical characteristics at the time it isto be fired, and each piece is there fore also fired at just the propertime after drying.

The rotary furnace 6 is diagrammatically illustrated in Fig. 1, and itis of the type described. in applicants said above mentioned copendingapplication. It comprises an electric furnace of circular design, theheating portion of which comprises an annular small passageway extendingaround the furnace. Inthis'annular passageway is adapted to rotate asuitable table provided with prongs for receiving the articles to befired. Suitable electric resistance elements'are placed in the furnaceat the desired point whereby the articles are progressively brought uptothe desired fusing temperature, maintained at such temperature for thecorrect amount of time and then progressively cooled until they reach aposition to be removed from the furnace. As this firing operation isuniform and continuous, each separate article fired will, at the time ofits removal from the furnace, be of approximately the same temperature.In practice, such articles as are removed from the rotary furnace, areof cherry red in color, and are of such a temperature that they veryeasily warp and sag, particularly if the articles are large and havebroad faces. The articles are taken from their horizontal position onthe supporting prongs in the furnace by means of forks which aredesigned to evenly support the articles at all points.

However, this is not always possible, and it is therefore sometimesdesirable to lay the hot articles on a fiat surface whereby they willstraighten, due to the inherent heat in the article, and thus be in acondition to handle properly when cool. It may be that even if thearticle warps the warped part may be brought into shape by subsequentfiring operations, but this is not always true and it usu- In order topositively prevent the article from being picked up too soon after it isremoved from the firing furnace, a straightening conveyer is provided,which may be designated '7. This conveyer is supported at the ends bymeans of suitable gears or rotors 8, whereby the conveyer iscontinuously moved in a closed path at a desired speed. The length ofthis conveyer 7 is proportioned according to the firing temperaturemaintained in the furnace 6, one end of the conveyer being positionedclosely adjacent the take-out aperture of the furnace, and the other endof the conveyer being positioned closely adjacent a conveyer 9, whichmay be termed a secondary cooling conveyer.

The articles, when they are removed from the furnace in their cherry redcondition, are then placed fiatly upon the straightening conveyer 7.This conveyer is provided with a plurality of heavy, fiat, shoes orslats 10 which present a continuous flat surface between the rotors 8.As the hot articles are positioned flatly on this conveyer, they willgradually straighten out, due to their inherent weight and temperature,and also gradually cool. The separate articles are maintained in thisflat condition the length of the conveyer and the conveyer is of suchlength that when said articles reach the end of the conveyer, they willhave cooled to such an extent that they will not be affected in theleast by the removal from the conveyer table by the operator.

This positively eliminates all sagging and warping of the hot articlesdue to any operator picking them up too soon, and it automaticallyinsures straightening of all the articles.

When the articles are removed from the straightening and coolingconveyer they are placed in upright position on the secondary coolingconveyer 9 and are conveyed back and forth whereby they are completelycooled, so as to be initially inspected and then conducted through thespray booth.

After the articles are sprayed they are immediately dried and fired, andthen sprayed, dried and fired again for the finishing operation. It willbe understood that between the second and third firing operations asimilar conveyer 7 may be utilized for positively effectingstraightening and cooling of the articles. The same is true after thefinal firing operation when the finally finished articles are stored orplaced upon racks. After this final firing operation, the article may beplaced directly on a cooling and straightening conveyer, just as isshown in Fig. 1, and therefore insuring positive straightening and thecorrect amount of cooling before being picked up and stored ortransported.

It will be understood that the conveyer elements 10 are preferablyheavy, whereby, in case any extra heavy sheet or article is fired and isslightly warped when placed upon the straightening conveyer, thatsuitable weight ing means may be utilized when effecting straighteningof the article.

It will be also understood that this interposition of the straighteningand cooling conveyer between the first and second firing operationscooperates directly with the spraying and subsequent firing operation,in that the articles are insured to be evenly and uniformly sprayed, asotherwise if the article were as to the firing of the enamel and thecontour of the surface.

Claims:

1. In an enameling mill of the type having a rotary furnace forconsecutively firing metal articles at a relatively high heat and meansfor receiving the fired articles, the combination with said firingfurnace and said receiving means of a conveyer positioned therebestween, one end of the conveyer being adjacent the outlet of the furnaceand the other end adjacent said receiving means, the surface of saidconveyer being relatively flat whereby to receive the hot fired articlesand to straighten the same, the length of the conveyer between saidfurnace and saidreceiving mean-s being such as to insure cooling andfixing of the straightened articles whereby to insure that the articleswill not be afiected when transferred from the straight ening conveyerto the receiving means.

2. In an enameling mill for metal articles, the combination offiringmeans for firing and delivering metal articles at a relativelyhigh heat, means positioned adjacent said delivering point for receivingand supporting said articles whereby they are straightened due tosaidsupporting surface, mean-s for moving said supporting means wherebymovement of the supporting surface will simultaneously cool said articleor articles thereon at or during the straightening step, and a secondarycooling means positioned adjacent saidsupporting means at such adistance from the delivering point of the hot articles to insure coolingand fixation of the articles before being transferred to said secondarycooling means.

In testimony whereof we aifix our signatures.

ALVIN G. SHERMAN. ALBERT MEADOWS.

